Spanning tree
Results 1 to 9 of 9

Thread: Spanning tree

  1. #1
    Senior Member
    Join Date
    Jul 2004
    Posts
    177

    Question Spanning tree

    Hi, i've here 3com equipment (3300, 4400 and 49xx switches) and i've to be sure of the paths that the information between clients and servers is following. I think that i've to activate spanning tree protocol in the switches... I know how it works, but i never implemented it before.

    I was googling for a while but i only got information about cisco equipment. I'm not able to find any 3com valid resource...

    Do you know where i could find it?

    Thank you!

  2. #2
    Just Another Geek
    Join Date
    Jul 2002
    Location
    Rotterdam, Netherlands
    Posts
    3,401
    It should work the same way (with some minor implementation details).
    The principle is the same.

    Is your network build redundant?
    STP is there to prevent "loops" in your network design or packets ariving twice (or more) at the destination. This can happen when everything is double connected (thereby creating redundancy).

    Making sure of the path the packets are traveling is a matter of correct routing.
    Oliver's Law:
    Experience is something you don't get until just after you need it.

  3. #3
    Senior Member
    Join Date
    Jul 2004
    Posts
    177
    And how can i configure routing in a LAN? All is driven by the MAC adresses learned by the switches, isn't it?

    I will explain a little bit more, the net here is not so complicated.

    There are 5 floors. The first one is where the servers are. Here, in the first, there is a 3com 3900 (Gigabit switch) that is connected to each switch on each floor (in the big ones we have more than one switch in the same unit with this "stack cable" thing). There is a 3com 3924 (the same that 3900 one but with 24 ports) where all the servers are connected also. Between the 3900 and the 3924 there is a cat6 cable.

    That i want to know is:

    -How can i be sure that the people is going to the servers in that way: switch in the floor -> switch that connect all flors -> switch where all the servers are connected.

    -If i put two cables between the switches will increase the bandwith? I can't use resilient links because STP... Is STP doing the work for me?

    Thanks.

  4. #4
    Just Another Geek
    Join Date
    Jul 2002
    Location
    Rotterdam, Netherlands
    Posts
    3,401
    If I understand correctly you have 1 flat broadcast domain?

    -How can i be sure that the people is going to the servers in that way: switch in the floor -> switch that connect all flors -> switch where all the servers are connected.
    It does. Rest assured it does. No worries. Only your broadcasts will be send to all switches and all ports. Unless someone or something f**ks up your switches (STP doesn't help you here).

    -If i put two cables between the switches will increase the bandwith? I can't use resilient links because STP... Is STP doing the work for me?
    Cisco calls this an etherchannel. You'll need to configure both ports to enable it. If you don't it'll be a redundant link (which will be 'blocked' by STP and unblocked if the other connection fails).
    Oliver's Law:
    Experience is something you don't get until just after you need it.

  5. #5
    Senior Member
    Join Date
    Apr 2004
    Posts
    1,130
    Using more than one port to increase bandwidth between is also callled "trunking".
    STP will find routes to connected everybody.
    However, be aware when u create "backup" path.
    For example, allways create a "tree", starting from your backbone.
    Never interconnect same leaves (dont create horizontal connections). If you create an "odd" connection, such as connect switch on 4h floor to switch on 5th floor, STP can "think" that is better than use "4th floor to backbone" and screw your performance.
    If u need backup links, allways put a new cable between dept switch and core switch.
    (man, its hard to explain without a paper to draw :P
    Meu sítio

    FORMAT C: Yes ...Yes??? ...Nooooo!!! ^C ^C ^C ^C ^C
    If I die before I sleep, I pray the Lord my soul to encrypt.
    If I die before I wake, I pray the Lord my soul to brake.

  6. #6
    Senior Member
    Join Date
    Jul 2004
    Posts
    177
    Yes i'm talking about 1 flat broadcast domain. It's a 23 bit mask net...

    Ok, then, if i connect the switches in star, the connections will find the "logical" path? What's doing STP? How i configure it?

    And if it is well configured and i put 2 cables between the "root" switch and another one, STP will stop one until the other fails?

    I'm sorry, but this is too low level for me, i never went bellow layer 2 before

    man, its hard to explain without a paper to draw :P
    Indeed, they will provide kind of dashboard in NETWORK forums

  7. #7
    Senior Member
    Join Date
    Apr 2004
    Posts
    1,130
    STP creates a tree, starting from root bridge (thats why is a tree)

    Since STP doesnt allow redudant paths (as old IBM bridging protocol provides), protocol will disable any path that cause a "loop".
    However, when one path goes down, STP will re-enable that one (the loop one).
    Its an auto-discover protocol. Just enable it and it will do the job by itself.
    When enabled, all bridges (all switch ports) will "elect" a root bridge and start to calculate costs and discover loop paths.

    When you need redundant paths, like between core and a office floor, you just use 2 cables between them. (2 ports on each side)
    STP will elect one as active and other one as disabled.
    If active fails, STP will re-enable the disable one.

    Its easier that you think.
    Meu sítio

    FORMAT C: Yes ...Yes??? ...Nooooo!!! ^C ^C ^C ^C ^C
    If I die before I sleep, I pray the Lord my soul to encrypt.
    If I die before I wake, I pray the Lord my soul to brake.

  8. #8
    Senior Member
    Join Date
    Jul 2004
    Posts
    177
    Ok, thanks, i understand a little bit more now... But i guess that i've to configure the parameters in the spanning tree protocol, and check that is activated in all the switches. And, how can i know who is the root?

    I attach the config page in the core switch, the other ones are similar.

  9. #9
    Senior Member
    Join Date
    Jul 2004
    Posts
    177
    I found this http://support.3com.com/infodeli/too...770-0baa06.pdf

    It doesn't talk about RSTP parameters but it's very interesting...

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •